The present invention relates to a time-division multiple access communication system which provides concentration by switching subscriber telephones to a smaller number of transmission facilities and provides deconcentration by switching the transmission facilities to the subscriber line terminals of an end-office telecommunication switching system.
A multiple access communication system as shown and described in Japanese Pat. No. 59-154828 comprises a central station and a plurality of terminal stations each serving telephone subscribers. The central station is connected to each terminal station by radio channels which are smaller in number than the subscribers. Each terminal station is provided with all switching functions necessary for providing switched connections for outgoing, incoming and intraoffice calls. These functions are implemented by a memory for storing dialed information, a decoder for translating the dialed information to determine a desired route to the central station and other complex circuitry. However, if the system of this type is to be connected to an end office (a telephone office at the lowest level of the hierarchy of the public telephone network) to serve as a "line concentrator" between the end office and the subscribers, each subscriber must have a corresponding line terminal in that end office. In such applications, all intraoffice calls must be routed through the radio transmission channels and folded back through the end office switching network to establish a connection between two subscribers for purposes of charging. For efficient utilization of the valuable common channels, the system disconnects the fold-back connection, establishes a local connection in the terminal station and switches the calling and called subscribers to the local connection when the called telephone answer the call. However, each terminal station must additionally be provided with a subscriber memory for storing call status information to detect intraoffice calls and identify the line numbers of the subscribers of intraoffice calls, and requires a complex switching matrix for establishing the local connection.